I would love to have been a fly on the wall during the pitch meeting for Dishonored. "Well, it's Deus Ex meets BioShock," someone undoubtedly said. "Oh hey, and let's throw in some Half-Life 2 'cause why not?"

It's a bizarre, eclectic blend, the type of combination that might seem too ambitious to work. But the resulting game is nothing short of a masterpiece.

Dishonored, developed by a star-studded crew that has history with all of the aforementioned titles, has drummed up a great deal of hype thanks to one lofty promise: you can play however you want. You can turn your character into a guard-stabbing slaughter machine, waging warfare on the grim city of Dunwall in bloody fashion. You can sneak along the rooftops and snipe down targets from afar. You can even go the whole game without taking a single life, an achievement that, while admirable, would probably be a little boring for your adroit assassin of a hero.

That hero, by the way, is a bodyguard named Corvo, forced to don a mask and go on the run after he's framed for killing the empress he was supposed to protect. Corvo is a trained killer armed with a number of weapons and items: in addition to a sword, crossbow, and pistol, he has access to grenades, sleep darts, explosive bolts, and quite a few other traps and gadgets. Early in the game, Corvo is visited by a spiritual being named the Outsider, a deity-slash-guardian who grants him a set of magical abilities—he can learn how to possess rats and slow down time, among other supernatural pastimes. To access these abilities, you have to collect special runes that are hidden in the nooks and crannies of Dunwall's abandoned apartments and sleazy brothels. You can use those runes both to earn new abilities and upgrade the ones you already have.

WHY: Where most games have strict rules and guidelines, Dishonored has suggestions. Suggestions that it encourages you to mess around with at every turn. Blending the do-what-you-want structure of Deus Ex with the masterful world design of BioShock, this game is really something special.

You'd think this sort of excessive strength would make the game too easy, but towards the latter stages of Dishonored, when you've mastered Corvo's powers and transformed him into a bona fide killing machine, he's still a glass cannon. Even on the lowest of the game's four difficulty levels, it's easy to get yourself killed if you're surrounded by guards, or you walk into the wrong room and find yourself face to face with one of Dishonored's mechanical monstrosities, like a gigantic watchtower that fires missiles at your face or a large electric pylon that will instantly turn you into a pile of ashes if you get too close.

The crème de la crème of Corvo's toolbox is Blink, a spell that you can use to teleport short distances both horizontal and vertical. I used this spell frequently and without mercy. I'd use it to bounce among exhaust pipes, sneaking into dusty old homes and raiding their rat-infested cabinets for goodies. I'd blink to get out of harm's way, to teleport to a hanging chandelier or window ledge where enemies couldn't reach me. I used it all the time. I cannot rave enough about this ability. It's liberating, empowering, and absolutely delightful to experience.

The tagline for Dishonored is "Revenge Solves Everything," and indeed, much of Corvo's story involves taking out bloody (or non-bloody) revenge on as many people as possible. It's a fun story, but its writers were clearly limited by the game's tight, mission-based structure (which ensures that the plot can only progress during downtime) and the fact that your hero, as a reflection of your personality, doesn't say a word. Far more interesting are the little details you'll find as you explore Dunwall: the snappy conversations between citizens, the posters advertising for old-fashioned shops and bars, the books and guides suggesting a much, much larger world than you'll get to see during the 15-20 hours it takes to beat Dishonored's main storyline.

Dunwall, which is set in some sort of twisted alternate version of the early 20th century, is a corrupt city, the type of place that's so unsettling, so horrifying, so completely and utterly nasty, you might not even mind painting its streets with blood. Corrupted both by human greed and a terrible plague that has killed a large part of its population, Dunwall is fascinating in its misery and squalor.

A large part of Dunwall's charm draws from the art. Oh, the art! The environments! Horrifying and grisly and bloody and beautiful, Dishonored's is a world that will stick with me for a long time. It's hard to go more than a few feet without finding something interesting to look at, whether it's a stone tablet laying out religious tenets for Dunwall's insane group of zealots or a crinkled flyer warning citizens that it's a crime not to report people who have the plague. Everything is detailed and gorgeous and lovely and vile.

Populating this heinous city is a group of artificially intelligent people who are as fun to watch as they are to kill. Guards will stomp rats and chat with one another as they patrol the city's streets and corridors. Soldiers will light up cigarettes and drink whiskey, cough violently and complain about the plague. Characters are disfigured and abnormal, their faces lumpy and misshapen, as if they were molded out of wax and then stuck under a broiler. In another game this might be discomforting; in Dishonored it feels just right. Few of the people in Dunwall feel like they're worth saving, and they look as corrupt as they act.

Perhaps as an inevitable consequence of Dishonored's complexity, its characters sometimes don't behave like they should. Guards might stand around and stare at you from the outside of a tunnel, for example, rather than crawling inside to chase you down. Enemy soldiers will react the same way to a nameless guard's corpse as they will to the bodies of their biggest leaders—that is to say, they'll get scared and shout things like "A body!" I also experienced a few random bugs during my playthrough: objects floating in mid-air, corpses disappearing, people moving in funky ways. Not unusual fare for a game published by Bethesda.

Still, it's always a blast to try to break things in a game like this. Your Dishonored experience will likely differ from mine, and you will likely come away from the game with interesting stories of how you possessed a fish and snuck underneath a moat to dodge a pack of marauding Tallboys, or how you threw a grenade in a last-effort attempt to disable a dangerous pylon, only to be shocked to find that it actually worked. Swapping Dishonored stories with Kotaku's Kirk Hamilton over the past week was almost as fun as the game itself. And for me, few gaming experiences have been more enjoyable than dropping into Dunwall and finding creative ways to take down enemies, sneak through streets, and get revenge.

Playing a video game usually feels like battling against a designer's mind. Can you figure out exactly how to get past this obstacle? Can you find the solution to this next puzzle? Can you move quickly enough to defeat this boss?

Dishonored is different. Playing Dishonored feels like entering a designer's playpen. You're given a set of tools and encouraged to experiment with them, to break them, to explore and adventure and read and fiddle and sneak and kill. Freedom never felt so good.